1. Field of the Invention
This invention relates to a catalyst for the gas phase partial oxidation of an organic substrate, a method for the preparation thereof, and a method for producing a partially oxidized organic compound using the catalyst.
2. Description of the Related Art
For the production of acrylic acid, it has been widely practiced on a commercial scale a method which adopts acrolein as a raw material and effects gas phase partial oxidation thereof with molecular oxygen in the presence of a catalyst. In the catalysts for use in this production of acrylic acid, the catalysts are mainly used which have molybdenum-vanadium as a main component. Patents which have issued to inventions covering molybdenum-vanadium type catalysts include those disclosed in JP-B-50-25,914, GB 1 488 889, GB 1 488 890, U.S. Pat. Nos. 3,773,692, 3,867,438, 4,414,412 etc.
While these catalysts for the production of acrylic acid have already reached the point where they exhibit yields of high levels, they are still required to offer further improved yields. The reason for this is that since acrylic acid is now produced on a large scale, even a slight improvement of yield brings a very high economic effect due to economization of raw material. Further, the improvement of such a catalyst in service life and durability brings about an extremely large economic effect.
Owing to this situation, the development of a catalyst for the production of acrylic acid which excels in catalytic qualities such as activity, selectivity, and service life constitutes a constant theme for researchers in the relevant technical field.
The gas phase partial oxidation of aromatic compounds or alkyl-substituted heterocyclic compounds are practiced widely on a commercial scale, such as the production of phthalic anhydride by the gas phase partial oxidation of orthoxylene and/or naphthalene, the production of maleic anhydride by the gas phase partial oxidation of benzene, the production of pyromellitic anhydride by the gas phase partial oxidation of 1,2,4,5-tetraalkyl benzene, and the production of an aromatic nitrile or a heterocyclic nitrile by the ammoxidation of an alkyl-substituted aromatic compound or an alkyl-substituted heterocyclic compound. Various catalysts have been proposed for use in the gas phase partial oxidation.
These gas phase partial oxidation catalysts have excellent properties of themselves. Nevertheless, the development of gas phase catalysts excelling in catalytic qualities such as activity, selectivity, and service life constitutes a constant theme for researchers in the relevant technical field.
An object of this invention is to provide a catalyst for the gas phase partial oxidation of an organic substrate which excels in catalytic qualities and enables the target product to be obtained stably in a high yield for a long time.
Another object of this invention is to provide a method for producing a partially oxidized organic compound by the use of the catalyst.
Yet another object of this invention is to provide a method of preparation suitable for the preparation of the catalyst.
According to the first embodiment of this invention, it provides a catalyst for the gas phase partial oxidation of an organic substrate which comprising a catalytically active component supported on an inert carrier, the carrier having at least one property selected from the group consisting of the water after the following treatment exhibits specific resistance of not less than 10,000 xcexa9.cm (25xc2x0 C.) in the case of producing an unsaturated aldehyde or an unsaturated carboxylic acid having not less than three carbon atoms and containing at least one double bond, and the water after the following treatment exhibits specific resistance of not less than 20,000 xcexa9.cm (25xc2x0 C.) in the case of producing an organic acid anhydride or a nitrile compound having not less than four carbon atoms:
(Method of Treatment)
In a conical beaker having an inner volume of 500 ml, 300 ml of a given carrier is placed and dried at 120xc2x0 C. for two hours and then the dried carrier and (amount of water absorption+220) ml of purified water added thereto are heated at 90xc2x0 C. under normal pressure for 30 minutes, wherein the amount of water absorption is represented as follows:
Amount of water absorption=A/B
wherein
A=300 (ml)xc3x97packing density (g/ml)xc3x97water absorption ratio (wt. %)/100 and
B=density of water (g/ml).
According to the second embodiment of this invention, it provides a method for the production of a partially oxidized organic compound which comprises effecting gas phase partial oxidation of an organic substrate or an organic substrate-containing gas with a molecular oxygen or a molecular oxygen-containing gas in the presence of the catalyst mentioned above.
Further, according to the third embodiment of this invention, it provides a method for the preparation of a catalyst for the gas phase partial oxidation of an organic substrate, which comprises supporting a catalytically active component on an inert carrier, the carrier having at least one property selected from the group consisting of the water after the following treatment exhibits specific resistance of not less than 10,000 xcexa9.cm (25xc2x0 C.) in the case of producing an unsaturated aldehyde or an unsaturated carboxylic acid having not less than three carbon atoms and containing at least one double bond, and the water after the following treatment exhibits specific resistance of not less than 20,000 xcexa9.cm (25xc2x0 C.) in the case of producing an organic acid anhydride or a nitrile compound having not less than four carbon atoms:
(Method of Treatment)
In a conical beaker having an inner volume of 500 ml, 300 ml of a given carrier is placed and dried at 120xc2x0 C. for two hours and then the dried carrier and (amount of water absorption+220) ml of purified water added thereto are heated at 90xc2x0 C. under normal pressure for 30 minutes, wherein the amount of water absorption is represented as follows:
Amount of water absorption=A/B
wherein
A=300 (ml)xc3x97packing density (g/ml)xc3x97water absorption ratio (wt. %)/100 and
B=density of water (g/ml).
The catalyst for the production of a partially oxidized organic compound according to this invention excels in activity, selectivity, and service life and enables the partially oxidized organic compound to be produced in a high yield for a long time.